Seoul, South Korea (CNN) -- Members of the South Korean military protested on the streets of the nation's capital Saturday, stating that they were angry that their country's government had not done enough to respond to recent shelling by North Korea.

One group of protesters gathered near the defense ministry building Saturday. The crowd clashed with police officers, some charging and kicking officers.

The protests come as tensions between the Koreas are growing.

The United States is sending the aircraft carrier USS George Washington to join South Korea's forces near the coasts of China and North Korea in a four-day drill military drill that starts Sunday.

The drill is set to begin five days after North Korea shelled a South Korean island, killing four South Koreans and wounding 15 others.